Ziram herbicide determination using a polished silver solid amalgam electrode

Abstract

The use of a polished silver solid amalgam electrode (p-AgSAE) and the square wave voltammetry (SWV) in the electroanalytical determination of Ziram herbicide in natural water samples is reported. The experimental and voltammetric parameters were optimized at 0.04molL−1 Brinton-Robinson buffer (pH 7.0), with a pulse potential frequency of 80s−1, pulse amplitude of 30mV, scan increment of 2mV and the cationic surfactant, cetyltrimethyl ammonium bromide, in the same molar ration of Ziram herbicide. In potential interval from −0.10V to −1.40V, the electrochemical redox process of Ziram occurred in two parts. In the first one, the Ziram complex is dissociated to anion radical and metallic cation, in a totally reversible redox process involving two electrons transfer. This electrons transfer, immediately initiate the subsequent reaction where the anion radical formed is converted to highly reactive dianion, in a reversible electron transfer. The dianion generated undergo an eletrophilic substituent by H+ ions, in a following chemical reaction. The second part corresponds to a quasi-reversible redox process from reduction reaction of the Zn+2 to metallic Zn. Analytical parameters such as: linearity range, equation of the analytical curves, coefficients determination, detection and quantification limits, recovery efficiency, and relative standard deviation for intraday and interday experiments were evaluated indicating that the voltammetric procedure using an p-AgSAE is suitable for determining any contamination by Ziram, minimising the toxic residues due to the use of liquid mercury or the adsorptive process relative to the use of other solid surfaces.